Introduction

Git rebase is a powerful tool for rewriting commit history, but when used incorrectly on long-lived feature branches, it can lead to severe issues such as merge conflicts, lost changes, and collaboration disruptions. Force-pushing after a rebase can overwrite commits that other developers rely on, causing history divergence and requiring manual intervention to recover lost work. This article explores common pitfalls of rebase and force-push in Git, debugging techniques, and best practices for safe usage.

Common Causes of Merge Conflicts and History Corruption

1. Rebasing a Long-Lived Feature Branch with Divergent History

Rebasing a feature branch that has already been pushed can lead to conflicts when the remote branch has additional commits.

Problematic Scenario

# Developer A
$ git checkout feature-branch
$ git rebase main

# Developer B (already made new commits to feature-branch)
$ git push origin feature-branch

Now, Developer A’s rebased branch has a different history from the remote branch.

Solution: Use `git pull --rebase` Before Pushing

$ git pull --rebase origin feature-branch
$ git push origin feature-branch

Using `git pull --rebase` ensures the latest remote changes are included before pushing.

2. Force-Pushing After a Rebase Overwrites Remote History

Force-pushing (`git push --force`) after a rebase can delete commits that exist in the remote repository.

Problematic Scenario

# Rebasing local branch
$ git rebase main
$ git push --force origin feature-branch

If other developers have based work on the old commit history, their local branches will be out of sync.

Solution: Use `git push --force-with-lease` Instead

$ git push --force-with-lease origin feature-branch

Using `--force-with-lease` prevents force-pushing if the remote branch has new commits.

3. Accidental History Corruption Due to Incorrect Interactive Rebase

Using `git rebase -i` incorrectly can delete commits if they are accidentally dropped during an interactive rebase.

Problematic Scenario

$ git rebase -i HEAD~5

If a commit is mistakenly removed from the interactive rebase list, it will be lost.

Solution: Use `git reflog` to Recover Lost Commits

$ git reflog
$ git reset --hard HEAD@{1}

Using `git reflog` allows developers to recover mistakenly dropped commits.

4. Merge Conflicts Due to Rebased Commits Appearing as New Changes

After rebasing, Git may not recognize common ancestors, leading to repeated merge conflicts.

Problematic Scenario

# Rebasing feature branch onto main
$ git rebase main

# Trying to merge back
$ git checkout main
$ git merge feature-branch

Git treats rebased commits as entirely new changes, causing unnecessary conflicts.

Solution: Use `git rerere` to Auto-Resolve Repeated Conflicts

$ git config --global rerere.enabled true

Enabling `rerere` caches conflict resolutions, reducing redundant conflict resolution efforts.

5. Accidental Rebase onto the Wrong Branch

Rebasing onto the wrong branch can mix unrelated changes and create a difficult-to-debug history.

Problematic Scenario

$ git checkout feature-branch
$ git rebase develop

If `feature-branch` was originally based on `main`, rebasing onto `develop` can introduce unintended changes.

Solution: Use `git rebase --abort` to Cancel a Bad Rebase

$ git rebase --abort

Using `git rebase --abort` allows developers to cancel an incorrect rebase before changes are applied.

Best Practices for Safe Rebasing and Force-Pushing in Git

1. Always Use `git pull --rebase` Before Pushing

Ensure local changes are up to date before rebasing.

Example:

$ git pull --rebase origin feature-branch

2. Prefer `git push --force-with-lease` Over `git push --force`

Protect against overwriting remote changes.

Example:

$ git push --force-with-lease

3. Use `git reflog` to Recover Lost Commits

Check previous commit states in case of accidental history rewriting.

Example:

$ git reflog

4. Enable `git rerere` for Efficient Conflict Resolution

Automatically resolve conflicts that have been fixed before.

Example:

$ git config --global rerere.enabled true

5. Abort an Incorrect Rebase Using `git rebase --abort`

Cancel an ongoing rebase if unintended changes occur.

Example:

$ git rebase --abort

Conclusion

Unexpected merge conflicts and history corruption in Git are often caused by incorrect rebasing, force-pushing, and interactive rebase mistakes. By using `git pull --rebase`, `git push --force-with-lease`, `git reflog` for recovery, and enabling `git rerere` for conflict resolution, developers can safely manage long-lived feature branches without disrupting team workflows. Following these best practices ensures a clean Git history and smooth collaboration.

FAQs

1. Why does `git rebase` cause conflicts when merging?

Rebasing changes commit history, making Git treat rebased commits as new changes, which can lead to unnecessary merge conflicts.

2. How can I recover lost commits after a bad rebase?

Use `git reflog` to find previous commit states and reset the branch to a safe point.

3. When should I use `git push --force-with-lease`?

Use it when rebasing a shared branch to prevent accidental history overwrites if the remote branch has changed.

4. How do I prevent rebase conflicts in long-lived branches?

Regularly rebase onto the latest `main` branch and use `rerere` to automatically resolve previously fixed conflicts.

5. What should I do if I accidentally rebased onto the wrong branch?

Use `git rebase --abort` to cancel the rebase and restore the original commit state.